a) Field of the Invention
The present invention relates to stabilizing systems for boats, and more particularly for a stabilizing system which better enables boats to make sharp turns, and particularly sharp turns at relatively high speeds where the roll of the boat (rotation about the longitudinal axis of the boat) is minimized.
b) Background Art
When some boats having a shallow draft are making relatively sharp turns at high speeds, instability can be a problem. In some instances and with some configuration of boats (if not many configurations), when the rudder or the motor is turned as to execute a sharp turn, the boat will lean into the curve/roll, with the side of the boat on the inside of the curve moving downwardly into the water, and the opposite side on the outside of the boat being raised upwardly from the water. In this situation, it sometimes happens that the rear portion of the boat will slide or “skip” laterally, and then may tend to right itself with the boat tilting back the other way with the other side portion of the boat being lowered into the water. Not only does this create undesired instability, but it also does not permit proper execution of the sharp turn. The present invention is designed to alleviate that problem.
By way of pertinent background previous prior art design such as that known in U.S. Pat. No. 6,520,107, the boat a tendency to “heel over” whereby the boat rotates about its longitudinal axis into the direction of the turn. This is undesirable in a situation where the boat is desired to remain in a substantially planar position about the longitudinal axis and in a situation such as where a firearm is mounted in the bow portion of the watercraft where the term, “guns on target” is necessary to complete combat operations and maneuvers. For the disclosure of the present invention is well adapted to keep the boat flatter and less rotation about the longitudinal axis of the boat (roll) in the course of a turn, particularly where high lateral accelerations are exerted on the boat.
One prior art method of lifting the stern portion of the boat is to use trim tabs which are essentially vertically downward extending surfaces that extend into the water and provide a vertical lift in the aft portion of the boat to level it out. These are hydraulic trim tabs that are always placed on the stem of the boat. It has been found that the trim tabs are inadequate to prevent rotation about the longitudinal axis of the vessel in particularly in high G and sharp turns which is necessary in certain maneuvers such as military maneuvers. Trim tabs have been wholly inadequate to maintain a roll which is here in defined as rotation about the longitudinal axis of the boat.
Other known prior art includes U.S. Pat. No. 5,611,295 (Stables) where in the introductory portion of the patent (column 1), there is discussed the problem of “spin out” which is indicated as a problem of personal watercraft due to their more forward center of gravity. There is provided on each rear side portion of the boat a pair of inner and outer plates 10 and 11, each outer plate 10 having a length which can vary from eighteen to thirty inches. In column 2, line 34, it is indicated that the outer plate 10 will extend below the bottom edge of the hull 15 by approximately one inch, but it is indicated that the device is not necessarily limited to that dimension.
The operation of this apparatus is discussed on column 3, beginning on line 21. It is pointed out (beginning on line 28) that a unique feature of the outer plate 10 is its shape, and it is stated that this eliminates a detrimental reaction known as “sticking” in the aircraft industry. Beginning on line 34, it indicates that as the outer plate 10 moves laterally while in the turn, if it were perfectly rectangular, a low pressure area down the center of the plate would form, and thus the lower pressure area would create a suction that would stick the plate to the water. Then, when the boat is coming out of the turn and returning to a straight course, the craft must be over-steered to break the plate loose. This results in a brief period of loss of control. The patent indicates that the sides of the outer plate 10 are not parallel, and this discourages the “alignment” of any fluid circulation and reduces the formation of the pressure area. It can be seen in viewing FIGS. 1 and 4, that the upper and lower surfaces and the front and rear surfaces are non-parallel with one another.
Also in FIG. 5, the outer plate is positioned at the side of the boat and is aligned so that in a frontal view this plate slants downwardly and slightly inwardly toward the center of the boat. Thus, it would appear that as one side of the boat dips into the water making a sharp turn, this slant off the vertical would become more pronounced.
Additional patents show various sorts of plates or stabilizers that are mounted to the boat so as to protrude into the water.
U.S. Pat. No. 6,546,884 131 (Rodriquez) shows a “jet propelled watercraft stabilizing system.” This shows what appear to be shaped more like fins that one would see commonly on a fish, with these fins protruding outward and downwardly from the rear side of the boat. In reading the patent, it would appear that the person steers the boat in large part by leaning to one side or the other and causing the fin to dip into the water. The angular position of the fins is adjustable and trim blocks are provided to accomplish the positioning of the fins at different angles.
U.S. Pat. No. 6,546,888 B2 (Bertrand et al.) shows stabilizing fins which are removably secured to either side of the small watercraft. FIG. 6 gives a rear view of the stabilizing fin, and it would appear to have more of an appearance of a right angle triangle with the hypotenuse of the triangle having a curve and one side of the triangle attaching to the boat.
U.S. Pat. No. 6,325,009 B1 (Schulz et al.) shows a sailboat having a dagger board that can be retracted or extended downwardly into the water on opposite sides of the boat to control side slip or leeway.
U.S. Pat. No. 5,273,472 (Skedeleski et al.) shows a flexible fin applied to the edges of a surf board for added stability.
U.S. Pat. No. 4,561,371 (Kelley et al.) shows a catamaran stabilizing structure where there is a stabilizing dagger board on each hull. The center board has a double-wing stabilizer with adjustable pitch.
U.S. Pat. No. 3,473,502 (Wittkamp) shows a pontoon boat with pontoons on opposite sides in something of a catamaran structure where there are keel-like elements, such as shown at 38, and one end of which is secured to the pontoon.
By way of general background it should be noted that when the boat is chinning the propeller portion of the motor is hitting “bad” or aerated water where the propellers are no longer in the higher viscous regions of regular water but in pure air or in air water mixture which has a lower density and lower counter force on the propeller causing an increase in the rpm's of the propellers. For example, when a propeller (or one of two propellers in a dual motor boat) is outside the water, it can reach very high rpm's (e.g. 6,000 rpm's). When this high velocity rotation reenters the water the momentum of the propeller as well as the applied torque from the motor can cause an abrupt acceleration thereby injuring the driver and passengers of the boat (such as breaking their tailbone and ribs). This is referred to as “chinwalking”. Therefore it is advantageous to have the boat maintain a substantially minimal roll during a relatively sharp high-speed corner. In an environment such as a personal watercraft (i.e. a jet ski) this is not an issue because such watercraft are propelled by a jet propulsion hydraulic system, not a propeller which is most commonly used in a propeller driven system.
It should be noted that in the normal operations of boats, when engaging in a turn there is a de-acceleration and an excessive roll. For terms of definition, a certain degree of roll (i.e. 7–20 degrees) which in normal boating craft is sufficient and in some cases desirable because the net thrust with the lateral centrifugal force in gravity is substantially in line with the planar surfaces of the boat such as seats and standing areas. However, in recent times where certain combat operations necessitate a substantially lower amount of roll during turns, this excessive roll (i.e. 7–20 degrees with regard to the horizontal plane) is undesirable. Therefore even in prior art controlled turns where the velocity is lowered and the amount of roll is such that it exceeds 20 degrees, in a military or law enforcement type operation this is undesirable. It has been found in recent times that maintaining the roll of the boat to a minimum (e.g. 20–5 degrees), a gunner at the bow of the boat can maintain “guns on target” and engage a potential threat on the sea or the body of water. Further, it has been found that these turns can be engaged at full throttle and at full speed (e.g. 50 mph and at least 35–40 mph) where the roll of the boat is minimized and a wash out does not occur. The phenomena and apparatus to accomplish these goals are discussed further herein.
It should be noted that the term “guns on target” is in reference to maintaining a bead on a target during operational maneuvers. One of these maneuvers comprise high speed turns to port and starboard directions. For example, the vessel with a 50-callber machine gun mounted in the bow is making a port turn (i.e. to the left). In a prior art watercraft, the watercraft vessel will rotate into the turn where the starboard lateral portion will raise up with respect to the water thereby blocking visibility off the starboard bow and starboard side in general. This is clearly unacceptable if a potential target is located in this area. In many types of operations where such a turn is conducted, the driver may be avoiding a collision with a potential target whereby maintaining visibility and the ability to maintain a site picture is of a highest requirement.
It should further be noted that an excessive chinning or chine walking where the roll of the boat is so excessive that the propellers intermittedly engage causing intermittent thrust it is extremely undesirable in operations to have because this induces a lack of control where the boat is unstable and unsafe potentially causing injury to the driver and passengers. It should be noted that chinning is a roll where the boat rotates inwardly toward the turn. Chinning occurs where the boat rotates at the longitudinal axis inwardly in the direction of a turn and can have catastrophic effects where in some cases a boat will rotate and snap back to the opposite direction (where the outer lateral portion of the boat violently snaps downwardly) and cause bodily injury to the passengers and driver of the boat. Further, chinning or chine walking can compromise the boaters' abilities to engage in their missions such as firing a heavy machine gun, “bumping a boat” or maintaining a high speed pursuit.
It should be further noted that another benefit by implying the fin system is the vessel will track better at a lower velocity with respect to the water where the aft portion of the boat will not swing around or drift in a turn when subjected to the centrifugal forces of the turn. Therefore, essentially the vessel will go where it is intended without drifting in a low speed tracking where the rearward portion of the boat kicks outwardly away from the direction of the turn.
Therefore, it is a goal to stabilize the boat in corners to prevent chinning and roll in the course of a high G-force turn under full throttle in extreme maneuvers.